check validity for to/from in sipmsg_validate
sanity check for contact header(s)
indentation with tabs, correct typos, remove escaped quotes. thank you Walter Doekes for the code review.
dialog: fix primary key when updating dialogs in REALTIME db mode

When updating rows in the dialog table in REALTIME db mode, the dlg_id
update key is not properly initialized (actually contains random data).

Reported by miko95 on GitHub
Closes issue #306
drouting: fix warning: "current_partition" may be used uninitialized in this function
Merge pull request #294 from tallicamike/feature-sipmsgvalidate-for-tofrom

sipmsgops: Additional "f", "t" and "c" flags for sipmsg_validate() which check To, From and Contact header integrity