This commit adds support for two separate modes of defining distance
between elements in PD's Linear Pattern.
1. Overall Length - which works exactly like it works before,
2. Spacing - which allows user to explicitly define distance (offset) between
features.
- Since realthunder's contributions some months ago, the 4 pattern features (mirror, linear, polar, mulitransform) can handle several features at once.
This PR allows to select multiple features when creating a pattern.
(This speeds up the workflow because at the moment one has to create the pattern with one feature and subsequently add more.)
- fix dialog issue that Add and Remove button could be active the same time
- use the keyboardTracking feature to avoid unnecessary recomputes (e.g. currently 3 recomputes when inserting "12.5" to the length field of linear pattern)
- fix wrong <extends> statement in .ui files (automatically spotted and fixed by Qt's Designer)
- remove StdDirection,StdAxis and StdMirrorPlane properties
- support sketch H_Axis, V_Axis, N_axis as valid references in patterns
- polish reference selection gui (unified for standard axes and custom references)
