Factor out JPEG support into a module
This is to make adding support for new formats easier.
See the file pic_jpeg.h for the description of the interface that each
image format must support.
Recognize the files with ".jpeg" extension
Bugfix for the issue #429
The function FileChooser:FullFileName() was calculating the position of
the item incorrectly, i.e. would work only on the first page in
filechooser. This would break copying/moving files to clipboard and also
renaming files from the second page and subsequent ones.
Comment out [currently] unused variables.
Merge pull request #430 from tigran123/clipboard

Bugfix for the issue #429
Merge pull request #428 from tigran123/pic-fmt

Factor out JPEG support into a module
Two bugfixes and a cleanup
1. When loading boolean settings we have to explicitly check for the
return of nil from the self.settings:readSetting() function and only
modify the default if the return value is NOT nil.

2. When closing the document we have to reset the settings to defaults,
otherwise their values are re-used on the next open.

3. The messages "Links on page ON/OFF" changed to
"Link underlines ON/OFF" because the old version gave two false
impressions: a) as if the action is pertinent only to the current page
(but in fact it is global for the entire document) and b) that we are
disabling the links whereas we are only disabling the show of underlines
under the links. The new message addresses both issues.
Override some of UniReader's defaults in PICViewer
For the picture viewer we want to disable showing grey boxes on page
overlaps and underlining of the links (because there aren't any).
Update the message in the help screen for Shift-L
Set show_links_enable=false by default for DjVu
Remove unneeded page redraw from showToc()
This is a leftover from the days of "Retrieving TOC..." message, so it
is no longer needed.
Merge pull request #432 from tigran123/settings

Settings etc
Cleanup Menu info for images.
1. Don't show document cache as there is no such thing for PICViewer
2. Show the image size (in K) in brackets next to the resolution as that
is where it logically belongs.
Cleanup of pic.c
1. Report the true size of the document cache (0).
2. Cut down the number of pointer dereferences in drawPage().
Merge pull request #433 from tigran123/pic-cleanup

PICViewer cleanup
Provide :setDefaults() for overriding defaults
Because we re-use the same instance of UniReader object (i.e. PDFReader,
DJVUReader, CREReader and PICViewer) we have to re-initialize the
defaults on closing the document. The clean way to do this which allows
to keep the default values in a single place is in a :setDefaults()
method which this commit provides, together with the example of usage in
DJVUReader and PICViewer.
Clarify the purpose of :setDefaults() method
Delete commands which make no sense for PICViewer
Disable 10-deg rotation and history commands
At the moment PICViewer does not support rotation by arbitrary angle
(only 90 degrees), so the commands Shift-J/Shift-K should be disabled.
Also, jump history (Back/Shift-Back) commands are disabled.
Merge pull request #435 from tigran123/pic-cmd

Delete commands which make no sense for PICViewer