Multi-selection operations (Copy and Erase)

[ajay_garg]

This is a part of feature at ::

 http://wiki.sugarlabs.org/go/Features/Multi_selection

[ajay_garg]

Attaching the patches ::

(Note that "0001-sugar-sl-3317.patch" patch must be applied, after applying the patch at  http://patchwork.sugarlabs.org/patch/1157/

[ajay_garg]

Latest patch at ::
 http://patchwork.sugarlabs.org/patch/1180/

(Dextrose) Commit link ::
 http://git.sugarlabs.org/dextrose/mainline/commit/d0930e04e3c65e98b5532f44b2de5c34f880aba7

[ajay_garg]

Patch v5 at
 http://patchwork.sugarlabs.org/patch/1183/

Commit Link
 http://git.sugarlabs.org/dextrose/mainline/commit/e2679fdfaec3d8af23aff2a37e057c3dd087d01d

Changes of version-5 over version-4

---

A. Temporary workaround for the dbus-timeout issue. Enclosed

metadata-copy, and metadata-write operations in a Try/Catch block,
so that ANY exceptions/errors are caught; while the operation
continues to proceeed.
Thanks Anish for catching that.

[ajay_garg]

Patch v6 at
 http://patchwork.sugarlabs.org/patch/1185/

Commit Link
 http://git.sugarlabs.org/dextrose/mainline/commit/42912f86cb88173d6574af0d8290a93de5ece979

Changes of version-6 over version-5

---

A. Any journal-entries with ".xo" extension, were being installed

even though it was only being selected/deselected (in both
single- and double- mode). Fixed it.
Thanks Anish and Sascha.

[ajay_garg]

Patch v7 at
 http://patchwork.sugarlabs.org/patch/1192/

Commit Link
 http://git.sugarlabs.org/dextrose/mainline/commit/2160b4d442bd2b1f8d63d8188c0ed2c6cd3592ef

=================================

Also, patch for check/uncheck icons at
 http://patchwork.sugarlabs.org/patch/1193/

Commit Link
 http://git.sugarlabs.org/dextrose/mainline/commit/29d9e5c299d85bf341208859192f69ea3de49024

[ajay_garg]

Changes of version-7 over version-6

---

A. Select-all/Select-None actions have been made in-memory. This

serves the following two purposes

(i) Now, the select/deselect actions are not persisted to disk. (ii) Major speedup in select/deselect operations.

The solution was figured out by Anish; I just did the mechanics of
coding, that's it ;)

Also, thanks to Sascha.

[ajay_garg]

Patch v8 at
 http://patchwork.sugarlabs.org/patch/1205/

Commit Link
 http://git.sugarlabs.org/dextrose/mainline/commit/22ee61af567acba7ee5fee1f656804a19e561684

Changes of version-8 over version-7

---

A. A minor change in "select_set_data_cb(self, column, cell, tree_model, tree_iter)"

in class "listview.py".

This UI callback function may be called, when the model is
still not ready.
Since this function just affects the checkbox (only a UI
change), so if the model is still not ready, it is safe to
return at this point.

Thanks to Anish for catching that.