New entry mode: rhythmic dictation

[Stemby]

A new input tool might be supported for this entry mode: the numeric keypad.

Key	LilyPond
0	1
1	2
2	4
3	8
4	16
5	32
6	64
7	128
.	.

As shown here, Alt might be used for rests, and Ctrl for slurs.

Example:

1. activate the "rhythmic dictation" mode by pushing a button
2. press 1 2 . 3 2 2 1 on the numeric keypad
3. Frescobaldi should show a2 a4. a8 a4 a a2

This implementations would represent the solution for closing the first part of #839 .

[AlexSchr]

Some time ago, I experimented with some way of using key modifiers for entering the rhythm during MIDI input. However, it would add a lot of complexity to the code.
I think the more "Frescobaldic" way to do this would be to add a menu entry like "Tools => Rhythm => Convert logarithmic to lilypond" which does the proposed mapping for the currently selected text.

[fedelibre]

I'm testing pull #1039, which solves the second part of #839.
Note replacement works well if you first enter the rhythms using a spacer rest or a fixed note; it doesn't work with note durations alone:

8  2  2 2 8  8 4  4 4 % doesn't work
s8 s2 s s s8 s s4 s s %works

But I agree that entering the durations using a numeric keypad would be much easier.

[Stemby]

Actually a spacer rest might be a better solution than a fixed A, for rhythmic dictation.