Fix fatal IndexOutOfBoundsException

The problem:

Configure the account (just an example -- problems can occur in other
configurations as well):
Message Format: HTML
Reply quoting style: Prefix
Quote message when replying: yes
Reply after quoted text: yes

Reply to a message that has a large quantity (20+) of \r\n scattered in
the body of its HTML version (not an unusual scenario).

Add a reply.  Save the message as a draft.  Go back & open the draft
again.  A fatal IndexOutOfBoundsException occurs.

The cause:

When the draft was saved, the X-K9mail-Identity header was computed and
added to the message, then the text of the message was processed with
MimeUtility.fixDraftTextBody, replacing all occurrences of \r\n with \n in
the quoted message before being saved in LocalStore, thus invalidating the
X-K9mail-Identity header.

The fix:

Remove MimeUtility.fixDraftTextBody and implement
MessageCompose$EolConvertingEditText instead.  Any message text placed in
an EolConvertingEditText widget is assured to have \n line endings.  Any
message text extracted from an EolConvertingEditText widget is assured to
have \r\n line endings.  The X-K9mail-Identity header will always be
computed correctly.

Issues thought to be related:  4782, 5010, 5634, 5725

As noted in some of the referenced issues, errors didn't always result in
a fatal exception, but instead with mixed up text.

Ref:  commit f9a35aeaeeae67bd88c3b253c25d06832ca7da73
More robust checking to prevent fatal IndexOutOfBoundsException

Even with the fix in the parent commit,  the X-K9mail-Identity header can
become invalid if, for example, a user creates a draft in K-9 Mail, then
edits the draft outside of K-9 Mail, then opens the draft again in K-9
Mail.

This commit assures that an invalid X-K9mail-Identity header will not
result in an IndexOutOfBoundsException.
Generally replace \n with \r\n when part of a message

This builds upon the efforts started 2 commits back where \r\n is used for
all message text and \n is only used when the text is inside an
EolConvertingEditText widget.
Remove \n from R.string.message_compose_reply_header_fmt

This string resource is used in two places -- both with and without the
linefeed at the end.  Instead of having a linefeed in the string and
having the code remove it if not needed, the linefeed is now omitted from
the string and the code adds it if needed.

Also, the line ending is changed from \n to \r\n.

Also, the string in the DE and FR locales had linefeeds at the start that
were removed so they match all the other locales.

(The string in the zh-rTW locale was left alone, since it had no
linefeeds.  It looks like that file has numerous instances where \n was
replaced with actual newlines, which is probably not correct.)
Don't add blank lines to composed messages if there is no quoted text
Remove newline in reply header of zh-TW translation
Merge pull request #400 from zjw/change_line_endings

Fix problems related to the saving and retrieval of drafts