[TASK] Change usage of t3lib_DB->sql_pconnect to t3lib_DB->connectDB

Currently many entry points that connect to the database use sql_pconnect
for that. This method is a low level sql method that skips hook initialization.
Also duplicate code was spread all over the entry points and are rewritten
to use the exceptions from t3lib_DB->connectDB.

Change-Id: I5b3cdecfed018be43236d1d54feac47a29333213
Resolves: #27954
Reviewed-on: http://review.typo3.org/3059
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Björn Pedersen
Reviewed-by: Thomas Maroschik
Tested-by: Thomas Maroschik
Reviewed-by: Susanne Moog
Tested-by: Susanne Moog