Support alternate color palette

[josephmckinsey]

Adds an alternate color palette:

1. You can set an environment variable PG_PALETTE which points to the color yaml file
2. You can use with_palette(f, file) or with_palette(f, load_palette(file)) and use it like with_logger. This doesn't work in a threaded context, see below.
3. palette kwarg argument to functions such as plot_fuel or match_fuel_colors.

More tests may be necessary, since I discovered that the palette use was very confusing, and plotly and gr had its own options. It's a bit unclear what a valid color palette that supports both looks like.

In particular, the default order is hard coded in the get_default_palette used by plotly.

Dependency Update

Requires NREL-Sienna/PowerAnalytics.jl#9 to be merged first, as some filtering functions were fixed on the PowerAnalytics side.

I'd suggest merging the packages in the future, even if they are logically separate:

• making changes always require changing both
• PowerGraphics.jl tests can serve as a test for PowerAnalytics.jl

[josephmckinsey]

A friend pointed out my code is not thread safe, so if we want concurrency, then global palette state will need to be significantly more clever. This applies if we use ENV or a package global variable.

It's apparently well-known that ENV is not thread-safe and gets propagated to contexts in weird ways:
JuliaLang/julia#34726 (comment)

There's apparently a library to fix this, along with a proposal to put it in stdlib, but it seems to have stalled for now. JuliaLang/julia#35833 and https://github.com/tkf/ContextVariablesX.jl

[jd-lara]

Bump to 0.4 once it is registered check JuliaRegistries/General#89039

[jd-lara]

add HydroPowerSimulations.jl