Add check to ensure the host has the imap libraries

[blobaugh]

If not do not allow connections

When adding the widget do not show the form elements

On any output display on the front end display that the imap libraries need to be installed.

Use one function to hold the error string. That way we can change it in one spot later, and even add something for debugging.

[pdclark]

Resolved in this commit: Replace IMAP class with PEAR Net_IMAP