Changes

General: simplified our fileReloaded() method interface (#1491).

General: added the fileSaved() method interface (#1491).

Sample view: don't do anything when a file has been saved (#1491).

Some minor cleaning up.

Slight update to our sample view documentation page (#1491).

Central widget: prevent some flashing.
Some flashing was indeed occurring when in CellML Text view and 
modifying a file from outside of OpenCOR. When going back to OpenCOR, we
were asked to reload the file. Then, to reload the file resulted in a

Editing and CellML Editing view plugins: don't handle the `fileSaved()`
interface (#1491).

Editing view plugin: simplified things a bit (#1491).

CellML Editing view plugin: reworked our approach to the
saving/reloading of a file (#1491).

Revert "CellML Editing view plugin: reworked our approach to the
saving/reloading of a file (#1491)."
This reverts commit c6659bb9b6471e55fa4171877e6491859be44ff4.

CellML Editing view plugin: reworked our approach to the
saving/reloading of a file (#1491).

Raw CellML view plugin: reworked our approach to the saving/reloading of
a file (#1491).

Raw Text view plugin: reworked our approach to the saving/reloading of a
file (#1491).

CellML Annotation view: fixed a small problem with the hiding of our
busy widget.
This is an indirect result of our work on issue #1492.

CellML Annotation view: slight improvement to the saving of a CellML
file to which we have removed some annotations.

CellML Annotation view plugin: reworked our approach to the
saving/reloading of a file (#1491).

CellML Annotation view plugin: reworked our approach to the
saving/reloading of a file (#1491).

Raw SED-ML view plugin: reworked our approach to the saving/reloading of
a file (#1491).

Editing view plugin: simplified things a bit (#1491).

Central widget: we need our central widget to be enabled before we can
give the focus to the new view.

Central widget: get the mode and view tabs to work fine again.
This was due to our work on issue #1481.

SED-ML Editing view plugin: reworked our approach to the
saving/reloading of a file (#1491).

Core plugin: reworked our approach to the saving/reloading of a file
(#1491).

Some minor cleaning up.

Some minor cleaning up.

Simulation Experiment view plugin: some work on reworking our approach
to the saving/reloading of a file (#1491).

Some minor cleaning up.

File classes: refactored a few things that were in our CellmlFile class
but not in our SedmlFile or CombineArchiveFile classes.

Simulation Experiment view plugin: reworked our approach to the
saving/reloading of a file (#1491).

Central widget: finally prevented our GUI from flashing when switching
views.

Central widget: finally prevented our GUI from flashing when switching
views.

Slight update to our downloads page (#1491).