Fix T38112: Rigid Body can't be created for objects with linked mesh

Make poll function for rigid body add operators less strict.
UV Unwrap: smart uv unwrap would fail still on some very small faces
Fix for inorrect use of BLI_utf8_invalid_strip, add assert to prevent it happening again.
Sequencer: prevent unknown scopes from crashing
Fix for RE_engine_begin_result using a NULL pointer
Text3d: improve error checking when pasting from files
Code Cleanup: de-duplicate text pasting which only used the first line
Cycles: Fix World Homogeneous volume setting, had no influence.

Thanks to "storm" for noticing this!
Add profile control parameter to Bevel.

Parameter controls concavity / convexity.
    <.25 means: concave inward
    .25 means: straight slanted
    >.25 means: concave outward
    .5 means: circular (the default)
    1 means: straight along original sides
For now, there is a hard lower limit of .15
because more work is needed to get decent
results in the range below that.

The profile is actually a superellipse, and the
parameter is 1/4 of the exponent in the implicit equation
for a superellipse, except at the extreme values of 0 and 1.
Code Cleanup: style edits to bevel and remove unneeded boundvert_rep_face call
Fix issues with float precision in numinput, like 'R 123' who would show additional 'noise' digits.

Expose float precision helper in UI_interface.h API, so that numinput can use this helper as numbuttons already do.

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D186
Fix for incorrect use of abs() in intersect_sphere_sphere_2d
Fix T38108: blender freeze in remembering operator properties.
Fix T38105: Action Editor refresh is missing when a keyframe is inserted in 3D view

 When yiz insert a keyframe (on a location keying set f.e.) in the 3D-view and you got an action editor open then the action datablock is  not changed (displaying only the button "new") until you hover the action editor with the mouse.

 Added a handler in the action_header_area_listener to handle this case

If non-obvious, some technical note about what the cause of the bug was and
how it was solved.
Fix T38074: sequence rendering gave "No camera" warning for other scenes that
didn't need a camera because they use only compositing nodes.
Cycles: workaround for noise performance regression in CUDA 5.5

Use manual ternary operation widening in grad(). Without it nvcc 5.5 produces multiple branch splits with very big branches (because of inlining). This solves 19% performance regression for BMW1M-MikePan.blend.

Also remove one redundant instruction in perlin SSE (when h == 12 or h == 14, then h is always >= 4).

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D190
Fix T38131: node link buttons (like for cycles in material properties) were not
giving correct colors with theme menu colors set to bright values.

Thanks to Denis Declara for finding the cause of this bug.
Fix crash cancelling command line render to AVI movie file.
Fix T38104: mathutils.cell_vector() always returns (0,0,0)

Reviewed By: brecht
Fix T38134: cycles viewport render not updating when adding a world volume shader.