Merge pull request #8 from einhverfr/import_double_render

Avoiding double render after import on failure
Fixes permission denied errors due to locking requirements
Fixing gl modification
Merge pull request #80 from einhverfr/lock_batch_function

Lock batch function
Merge pull request #82 from ehuelsmann/master

Fix #1130.
Merge pull request #84 from ehuelsmann/master

Fix session handling, #1163 and #1164.
Merge pull request #17 from ledgersmb/master

sync over master branch