feat(FEC-8176): restructure media config

[dan-ziv]

Description of the Changes

Restructuring media config to:

ProviderMediaConfigObject = {
  session: ProviderMediaConfigSessionObject,
  sources: ProviderMediaConfigSourcesObject,
  plugins: { [plugin: string]: Object }
};

where:

ProviderMediaConfigSessionObject = {
  partnerId: number,
  uiConfId?: number,
  ks?: string
};

ProviderMediaConfigSourcesObject = {
  dash: Array<ProviderMediaSourceObject>,
  hls: Array<ProviderMediaSourceObject>,
  progressive: Array<ProviderMediaSourceObject>,
  duration: number,
  type: string,
  id: string,
  poster: string | Array<Object>,
  dvr: boolean,
  metadata: ProviderMediaConfigMetadataObject
};

ProviderMediaConfigMetadataObject = {
  name: string,
  description: string
};

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