More keyboard shortcuts

Following #25, here is more keyboard shortcuts suggestions.

I tested all shortcuts to verify that doesn't create conflicts with current ones, I hope it's good. :)

## Windows

- **Hide/Show editor window**: `ctrl` + `e`
- **Hide/Show objects window**: `ctrl` + `b`
- **Hide/Show console window**: `ctrl` + `k`
- **Hide/Show tracetrack window**: `ctrl` + `t`
- **Hide/Show variables window**: `ctrl` + `r`
- **Hide/Show CQ object inspector window**: `ctrl` + `i`
- **Hide/Show log window**: `ctrl` + `L`
- **open cadquery documentation**: `F1`
- **open settings window**: `ctrl` + `,`

## View

- **Toggle wireframe view**: `ctrl` + `w`
- **iso view**: `ctrl` + `5(pav. num.)`
- **top view**: `ctrl` + `8(pav. num.)`
- **bottom view**: `ctrl` + `2(pav. num.)`
- **front view**: `ctrl` + `1(pav. num.)`
- **back view**: `ctrl` + `3(pav. num.)`
- **left view**: `ctrl` + `4(pav. num.)`
- **right view**: `ctrl` + `6(pav. num.)`
- **fit view**: `ctrl` + `0(pav. num.)`

## Tools

- **export as STL**: `F6`
- **export as STEP**: `F7`
- **take screenshot**: `ctrl` + `print screen`
- **open recent file** (can also be added to File menu): `ctrl` + `shift` + `o`
- **go to** (open a popup allowing user to type a line number, can also be added to Tools menu): `ctrl` + `g`

## Editor

- **toggle comment and go to the next line** (add `#` at the beginning of the line, or removing it if already exist): `ctrl` + `/`
- **delete line**: `ctrl` + `y`
- **select all current line**: `ctrl` + `h`
- **duplicate line or selection**: `ctrl` + `q`
- **move content view up, without moving text**: `ctrl` + `up`
- **move content view down, without moving text**: `ctrl` + `down`
- **move up line**: `ctrl` + `shift` + `up`
- **move down line**: `ctrl` + `shift` + `down`
- **increase font size**: `ctrl` + `+` / `ctrl` + `wheel up`
- **decrease font size**: `ctrl` + `-` / `ctrl` + `wheel down`