GmEntry: Added Ekiga.net/im regexes.
GmEntry: Fixed entry validation when allow_empty is FALSE.

The GmEntry was validating despite allow_empty was FALSE when there was
no Regex.
GmEntry: Fixed regexes.
GmEntry: Fixed more regexes.
Form: Added Ekiga regex support.
Forms: Added support for Ekiga URI fields.
Assistant: Cleanups.

- Removed deprecated stuff.
- Ported to GmEntry.
- Changed Ekiga.net and Diamondcard accounts pages so that they
  represent to data presented to the user when registering:
  a) a SIP address instead of a user name for Ekiga accounts
  b) numeric account ID and PIN codes for Diamondcard
EkigaApp: Remove assistant window menu entry.

The assistant should be shown on upgrades only.
Assistant: Fixed FIXME.
OpalBank: Uniformised Ekiga & DiamondCard creation with signup.

Changed Ekiga.net and Diamondcard accounts creation so that it
represent to data presented to the user when registering:
a) a SIP address instead of a user name for Ekiga accounts
b) numeric account ID and PIN codes for Diamondcard
OpalBank: Improved Ekiga & DiamondCard account Actions.

Several changes here:
- If there is already an Ekiga.net account, we do not provide an action
  to create another one.
- If there is already a DiamondCard account, we provide actions to
  consult/recharge/... it.
TODO: More things to do.