Add member functions to basic Qt types in Rust

[LeonMatthesKDAB]

• Add missing member functions to types cxx-qt-lib: add member functions #416
• Consider if we should adapt the Rust API to be "safe" / less Qt-like (eg QRectF set_x)

Original Description
Types like QPoint have a lot of member functions, as well as operators (i.e. +,-,/,*) that make them a lot more useful. We should give Rust access to these as well.

[ahayzen-kdab]

Note that this is related to #53

[LeonMatthesKDAB]

Note: QRect's interface should propably not mimic Qt directly. set_x and set_y will change the width and height, which is not at all obvious/expected behavior. So we should improve on Qt in this regard, and come up with our own, safer interface.

[ahayzen-kdab]

Also ensure that we are using CXX where we can.

Eg

#[rust_name = "qurl_to_qstring"]
fn qurlToQString(url: &QUrl) -> QString;

could probably just be

#[rust_name = "to_string"]
fn toString(self: &QUrl) -> QString;

[ahayzen-kdab]

Also ensure that we are using CXX where we can.

Eg

#[rust_name = "qurl_to_qstring"]
fn qurlToQString(url: &QUrl) -> QString;

could probably just be

#[rust_name = "to_string"]
fn toString(self: &QUrl) -> QString;

We can't in this place as toString has an optional parameter. So we could have to provide that in Rust for it to work with CXX etc.

[ahayzen-kdab]

Also note that QDateTime it would be useful to link up the static methods like QDateTime::currentDateTime(), otherwise might have static methods that could be useful too.

[ahayzen-kdab]

Closing via #416.