Changed rmc_isGxGGA to be called gga_isGxGGA for consistency

[bismurphy]

Hi,

I've gone through all the code of this library and changed the rmc_isGxGGA functions to be called gga_isGxGGA. The RMC functions rmc_isGxRMC are untouched. I've just changed the prefix on the GGA functions to be gga rather than rmc, since they have nothing to do with RMC strings. For the sake of consistency and readability, I believe the GGA functions should be called gga. I suspect the fact that they start with rmc is a matter of old copy-pasted code sticking around and renaming them would aid the codebase in being more self consistent and comprehensible.

I realize this would make new versions fail to be backward compatible with old code which may use these rmc_isGxGGA functions. However, it seems unlikely that many users would be using these, since primarily the identification of commands is handled within the library itself, and given that I've already changed all the calls within the library to use the new "gga_" versions, this incompatibility should be minor.

Thank you for considering this pull request. If approved, I hope to also add other NMEA strings to this library, including GPGSV.

[codecov-commenter]

Codecov Report

Merging #46 (581c6f6) into master (ac48385) will not change coverage.
The diff coverage is 72.72%.

@@           Coverage Diff           @@
##           master      #46   +/-   ##
=======================================
  Coverage   91.35%   91.35%           
=======================================
  Files          10       10           
  Lines         370      370           
=======================================
  Hits          338      338           
  Misses         32       32           

Impacted Files	Coverage Δ
src/nmea/GxRMC.cpp	97.72% <ø> (ø)
src/nmea/util/checksum.cpp	100.00% <ø> (ø)
src/nmea/util/common.cpp	100.00% <ø> (ø)
src/nmea/GxGGA.cpp	78.30% <25.00%> (ø)
src/ArduinoNmeaParser.cpp	97.95% <100.00%> (ø)
src/nmea/util/gga.cpp	100.00% <100.00%> (ø)

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[aentinger]

Thank you very much for your PR @bismurphy 🚀 , this was indeed a copy-paste-error 🙇 .