installation: pip requirement version updates

* Updates requirements.txt with specific versions for all requirements.

* Updates mysql-python to 1.2.5 to make it work with the new pip.

* Changes the requirement from PIL to Pillow as PIL is abandoned.

Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
Merge branch 'maint-1.0' into maint-1.1

* maint-1.0:
  installation: pip requirement version updates