Remove upper bound on email TLD in emailRegexPattern.

The suggested solution by Diego was to make the limit 10, but making it
unbounded probably makes more sense. It lets people use custom TLDs in
local delivery / email testing without having to worry about length.
Make emailRegexPattern case insensitive.
Update comment for emailRegexPattern.
Change the using the CASE_INSENSITIVE flag in compile.

This should make the case insensitivity of the pattern more visible to
someone else who is looking at the code.
Merge pull request #1640 from lift/msf_issue_1634

This resolve issues with emailRegexPattern not being up to date w.r.t. new TLDs longer than four characters and being case sensitive.