Big refactoring of MediaSetAccess

Big refactoring of MediaSetAccess

- deprecate MediaSetAccess::provdeOptionalFile
- remove the mess of boolean cached, checkonly and stuff.
- For non-interactive (except for media change) there is a flag
  NON_INTERACTIVE which is accepted by provide*
- Downloaders don't need doesFileExist anymore.
- Exceptions are thrown. If you need ignore functionality, Fetcher
  has it, using OnMediaLocation::optional()
- refactor MediaSetAccess provideFile, provideDir in one common function
  removing tons of duplicated code

Pending/Next: refactor doesFileExist somehow (may be templating)
Fix doesFileExist in aria (may be with a curl external cmd line
implementation) using the following command line options

curl -I
-A agent
--basic
--digest
--connect-timeout
--cookie-jar
--anyauth
header -H "Host:"
--location
--no-keepalive ?
--proxy-basic / digest /negotiate
--proxytunnerl
-r 0-1
--user <user:password>
--proxy-user user:pass
--proxy <proxyhost[:port]>