o.e.email.ui: Move image snapshot and dialog in another UI Runnable

Fixes #241: On Linux, context menu which invoked the email action was
still visible and thus included in BOY screenshots
o.c.email.ui: Check for empty 'from:', 'to:' in ELog Dialog

Prevent 'OK' unless both fields contain something.
o.c.email.ui: Update version number
o.c.opibuilder, beast.ui, trends.databrowser: Clear default email

When users send screenshots or alarms via email, they now need to enter
a "from:" email address. The default values, e.g. "opi@css", didn't tell
the recipient who sent the email, making it hard to reply.

Sites who want to use default 'From:' email addresses can add this to
their site-specific plugin_customiation.ini (as before).
Merge pull request #313 from ControlSystemStudio/bugs_email

Bugs email: Fixes #241 and #312