Return input temperature units for LCL/LFC/EL temperature, disallow LFC if EL below LCL

[zbruick]

Description Of Changes

First, allows for return of LCL/LFC/EL temperature in the units of the input temperature. There may still be a bug in SkewT.plot that I need to investigate more, as I don't think things are getting auto-converted to the same units when you plot multiple things.

Second, this disallows a LFC below a LCL when an "EL" is also below the LCL. This bug was causing CAPE to calculate as the LFC was being adjusted to the LCL, and it didn't see an end to the profile (ending up in very large values of negative CAPE).

Checklist

• Closes most_unstable_cape_cin throwing negative CAPE values #1167 and closes LCL/LFC/EL temperature always returns Celsius #1170
• Tests added

[am-thyst]

these changes have caused the following error when calculating CAPE as mentioned in #1167:

Traceback (most recent call last):
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/sharedmem/sharedmem.py", line 294, in _slaveMain
    self.main(self, *self.args)
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/sharedmem/sharedmem.py", line 628, in _main
    r = realfunc(work)
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/sharedmem/sharedmem.py", line 703, in realfunc
    else: return func(i)
  File "/var/spool/torque/mom_priv/jobs/255664.rdf-xcat.SC", line 69, in cape_func
    cape, cin = most_unstable_cape_cin(vl_lst, prof_t, prof_td) # muCAPE calculation
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/metpy/xarray.py", line 487, in wrapper
    return func(*args, **kwargs)
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/metpy/units.py", line 312, in wrapper
    return func(*args, **kwargs)
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/metpy/calc/thermo.py", line 1797, in most_unstable_cape_cin
    return cape_cin(p, t, td, mu_profile)
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/metpy/xarray.py", line 487, in wrapper
    return func(*args, **kwargs)
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/metpy/units.py", line 312, in wrapper
    return func(*args, **kwargs)
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/metpy/calc/thermo.py", line 1431, in cape_cin
    parcel_temperature_profile=parcel_profile)
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/metpy/xarray.py", line 487, in wrapper
    return func(*args, **kwargs)
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/metpy/units.py", line 312, in wrapper
    return func(*args, **kwargs)
  File "/nerc/n02/n02/amethyst/minic/envs/newenv/lib/python3.6/site-packages/metpy/calc/thermo.py", line 451, in lfc
    if el_pres > this_lcl[0]:
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()"

[zbruick]

Ah, thanks for checking that. I'll go back and fix the code to only check one value there.

[dopplershift]

Looks good. LFC logic is getting a bit unwieldy, but at least we have a good test suite for some day refactoring it.

Ignoring Code Climate.