feat(FEC-12700): Make the player colors configurable from studio

[JonathanTGold]

Description of the Changes

1. Organizing the player's palette (and add some new colors)
2. Moved all configurable colors from a static (sass) variable to dynamic (css) variable
3. Added logic to calculate the secondary colors from the primary color (so that a user can only choose the primary color in the studio and the secondary ones will be derived from the primary one)
4. move the date-url of dynamic SVG icons (Those whose color changes in active mode to the color of the main color) to a variable so they can be changed at runtime (our current icons infrastructures uses sass functions to generate the data-url which are not useful at runtime but only at compile time)
5. add theme manager service that get the user configured style and apply the style

related pr: kaltura/playkit-js-ui-managers#18

solves: FEC-12700

CheckLists

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• test are passing in local environment
• Travis tests are passing (or test results are not worse than on master branch :))
• Docs have been updated

[SivanA-Kaltura]

@JonathanTGold how would a plugin access the new values now ? what refactor should be made if a plugin was accessing the values through the js object ? (KalturaPlayer.ui.style)

[semarche-kaltura]

@JonathanTGold how would a plugin access the new values now ? what refactor should be made if a plugin was accessing the values through the js object ? (KalturaPlayer.ui.style)

@semarche-kaltura the new values accessed as css vars for example: background-color: var(--playkit-primary-color)
Regarding the access of style in JS all the same as before except color variables that was deleted form variables.sass file
(that should be replaced by css var syntax in the css files)

V7 plugins uses new style variables (changes already implemented, waiting till current PR got merged and deployed). No issues found with using new styles variables.