Add light palette support

[pcdiem]

Description:

Light palette support adds the ability to specify a palette of colors to use instead of the standard color wheel and fixed colors. The Palette command specifies the list of colors to use. The list is allocated dynamically and is not stored in the settings so it is not preserved across restarts. Once a palette is specified, the Color<1,2> and Scheme<2,3,4> commands use the colors in the palette. The palette is cleared using the Palette 0 command.

Commands

Command	Parameters
Palette	0 = Clear the color palette <color>[ ...] = Set the list of colors to be used by the Color<1,2> and Scheme<2,3,4> commands with each color separated by a space

Checklist:

• The pull request is done against the latest dev branch
• Only relevant files were touched
• Only one feature/fix was added per PR.
• The code change is tested and works on core Tasmota_core_stage
• The code change pass travis tests. Your PR cannot be merged unless tests pass
• I accept the CLA.

[s-hadinger]

Nice. I understand that you are not consuming any space in Settings, hence you need to set again palette after reboot. I prefer it this way.