Sending last second message as quoted content

Each of its lines are prefixed with `> ` sign. It is then added to the end
of script
Convert new lines to html equivalents

Now E-Mails are send as HTML content type so it content should be in
proper HTML format

\n will convert to <br />
\n\n will convert to new paragraph
Refactored classes/class-supportflow-emails.php
Refactored code
Sanitizing ticket reply before sending in E-Mail
Loading cron schedule and registering cron after `init` action

At this moment both WP and plugin are initialized so it can now access
plugin data if required
Allow to change cron interval using a filter

Fixes #195
Methods accidentally called as functions
Merge branch 'master' into quote-outgoing

Conflicts:
	classes/class-supportflow-emails.php
Merge branch 'master' into cron-interval

Conflicts:
	supportflow.php
Setting details meta box as high

This is to display it as top sidebar by default

Fixes #199
Merge pull request #205 from VarunAgw/cron-interval

Filter the cron interval so it can be easily customized.
Merge pull request #206 from VarunAgw/details-box

Make the Details metabox appear before other metaboxes.
Corrected typo
Splitted meta_box_details method into sub-methods
Merge pull request #207 from VarunAgw/details-box

Modularize meta_box_details()

Fixes #203
Merge pull request #190 from VarunAgw/quote-outgoing

Quote previous message in replies to add context.
Determining $current_status_id before using
Merge pull request #210 from VarunAgw/meta-box

Determining $current_status_id before using

Fixes #208
Correct reply addition time were not shown