Allow embedding custom UI config in index.html

[yurishkuro]

For #489

$ cat yy.yaml
x: abcd
z:
  - a
  - b

$ go run ./cmd/standalone/main.go --span-storage.type=memory --query.ui-config yy.yaml

replaces

<!-- JAEGER_CONFIG = DEFAULT_CONFIG; -->

in index.html with

<!-- JAEGER_CONFIG = {"x":"abcd","z":["a","b"]}; -->

TODO:

• tests
• UI version that includes the config var in index.html

[coveralls]

Coverage decreased (-0.4%) to 99.644% when pulling e241533 on ui-config into a7f203b on master.

[coveralls]

Coverage remained the same at 100.0% when pulling b026119 on ui-config into a7f203b on master.

[coveralls]

Coverage decreased (-0.05%) to 99.954% when pulling 4b05d88 on ui-config into a7f203b on master.

[black-adder]

change this to: "JAEGER_CONFIG = DEFAULT_CONFIG;" to be a more accurate fixture?

[yurishkuro]

how is it more accurate? The regexp ignores the whitespace.

[black-adder]

s/unmarshall/unmarshal

[coveralls]

Coverage remained the same at 100.0% when pulling 45f377d on ui-config into a7f203b on master.

[coveralls]

Coverage remained the same at 100.0% when pulling cdce79b on ui-config into a7f203b on master.

[coveralls]

Coverage remained the same at 100.0% when pulling e9f47fa on ui-config into 7f28c77 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling b557609 on ui-config into 256d7d2 on master.

[coveralls]

Coverage decreased (-81.3%) to 18.667% when pulling 72c09d1 on ui-config into 256d7d2 on master.

[pavolloffay]

Now it fails without UI. Before it was working. Workaround is to create empty index.html or do not include static handler if flag is empty

#493 uses query as a docker container, when xdock is executed it builds all images, Now we have to build UI which takes significant time.

[yurishkuro]

let's discuss on #497