Use Qt designer for the preferences dialog

Use the Qt Designer for designing the preferences dialog instead of
doing that manually in code.
Implement MainWindow::deleteTablePopup()

Implement the code to delete a table by using the context menu.
Fix identation
Use a Qt Designer form file for the main window

Use the Qt Designer to build the main window form.
Handle create table action
Set the needed Qt modules properly in the project file
Get rid of addfieldform

Get rid of the addFieldForm class and dialog and use the editFieldForm
instead.
Also fix the window caption of the editFieldForm dialogs called by the
editTableForm to show the correct table name.
Fix last commit
Use a Qt Designer form file for the editFieldForm dialog

Design the editFieldForm dialog in Qt Designer.
Also add custom field type support and fix some other issues.

The dialog is still doing nothing because support for modifying columns
is still missing in the SQLite interface.
Remove the addFieldTypeForm dialog

Delete the addFieldTypeForm dialog which appears to be quite useless.
It's not needed by editFieldForm anymore and would probably never been
of any use at all.
Create Qt Designer form for editTableForm dialog
Get rid of renameTableForm dialog

Delete the renameTableForm class and dialog. They are basically useless
as their functionality can (and has been) easily be integrated into the
editTableForm.
Fix a number of bugs

Fix bug when closing the editFieldForm.
Fix bug that not always the correct database object was used.
Fix bug that changed field type when changing field name in editTableForm.
Fix editFieldForm to work correctly for newly added tables
Fix input validation of custom field type field
Clean up code, especially includes

Clean up the entire code a bit, especially by deleting unneeded defines
and includes. This should make the code a bit clearer and faster to
compile.
Always show all rows in table view of browse tab

Always show all rows of the current table in the browse tab of the main
window instead of limiting it to a 1000 per page.
Change the functionality of the buttons and inputs to change the page
accordingly.

Limiting the number of rows to a 1000 was probably done for performance
reasons but is a killer in terms of usability. And as we'll probably
move sooner or later to a model-view architecture that loads data on
demand, the performance when opening large tables will be more than
restored anyway.
Add modify field action to toolbar
Do not reload not needed information when changing the current tab

Do not query the table selected in the browse data tab when changing to
the database structure tab and vice versa.
Merge editTableForm and createTableForm

Add the functionality needed to create new tables to the editTableForm
dialog.
Delete the createTableForm as it is no longer needed, also delete its
semi-finished replacement createTableDialog.
Fix not working add column function and as usual some other bugs here
and there.