Support creating src artifacts from internal (tqtc-) qt5 submodules

Currently we have to create customer specific src packages from certain internal tqtc-qtbase, tqtc-<submodule> repositories. This is now done more or less manually using Jenkins. This process is prone to human errors and takes unnecessary manual effort.

We really should use only one tool (i.e. Coin) to create all release artifacts.

We tested this with Coin followingly:

1. create customer specific branch for (tqtc-)qt5.git
2. edit (tqtc-)qt5.git's .gitmodules file
   1. replace qtbase.git with tqtc-qtbase.git + customer ref
   2. replace <submodule>.git with tqtc-<submodule>.git + customer ref
3. Coin UI -> Schedule build
   1. Test configurations: select "License check" configuration
      (this should be enough to produce src artifacts only)

RepositoryManager fails with reading/parsing qt5.git's .gitmodules as there appears to be some logic that can not take into account tqtc-<submodule> namings.