Fix incorrect modification of bytea data when updating rows that contain bytea columns.
Based on the POC patch from ioguix.
This fixes SF Bug # 3243916.
fix typo
reword information around statistics collector. based on bug report SF #3602305
Add plugin hook 'head'.

Allows to add tags in <head /> from plugins
Add plugin hook 'logout'.

Allows to perform actions before beeing logged out.