Update .gitignore

Ignore auto-generated files that result from
"android update lib-project" (which is invoked within "ant debug").

Some of the plugins (library projects) already have their own
.gitignore file which includes the exclusions made here.  This
commit assures that the exclusions are applied to *all* plugins,
regardless.

This, of course, has no effect on files that have already been
intentionally checked into the git repository (such as the main
build.xml).
Remove ant.properties

The properties currently therein are duplicates of those in
project.properties.

The build.xml file first loads properties from ant.properties, then from
project.properties, so ant.properties is redundant.

The file's existance was a maintenance issue.  The past couple times
when the property "target" was updated in project.properties, the
property was overlooked in ant.properties, so ant builds would fail when
Eclipse builds would succeed.
Account preferences clean-up

There were a number of preferences that were not being removed
from the preferences DB when an account was deleted, so they
would remain there forever.

There were a few attempts to remove preference keys from the DB where
the keys were obsolete and not in use for some time.

Certain obsolete preferences were not modified:
mUuid + ".name"
mUuid + ".email"
mUuid + ".signature"
mUuid + ".signatureUse"
These were in use before implementing multiple identities, and are still used
as a fallback for old accounts without multiple identities configured.
Use a locale-specific date in the header of a quoted message

Also, include the sent-date in the header when using
the "prefix" quote style.  "Be like mutt" (and gmail,
and thunderbird)

Also, the quoteOriginalHtmlMessage method was using the mSourceMessage
field in various places when it should be using its originalMessage
parameter.

Related issues:  2249, 3456
Fix POP3 STLS command

The server response needed to be retrieved.

Thanks to Paul Durrant:
https://groups.google.com/d/msg/k-9-mail/0XHNNMR1TQ4/yExsr7nvJQwJ
Revert "Add work-around for Asus Transformer WebView display bug"

This reverts commit 78428e287bae6739b0df9fd9ca78ef7c2daaa893.
Merge pull request #437 from zjw/misc_clean_up