Merge branch 'polyline_pointsize' into 'master'

use pointsize from material dialog for polyline spheres

A few adjustments were needed regarding #54 

- switch default draw mode to POINT_SPHERE_SCREEN instead of POINT_SPHERE, because this is the more intuitive mode

- POINT_SPHERE takes the radius from the material dialog

- The material dialog spinboxes for point size and line length are converted to QDoubleSpinbox to allow for floating point values. A world scale radius of 1 in POINT_SPHERE mode is already too big, so values between 0 and 1 are needed here

See merge request !112
9 jobs for master in 82 minutes and 44 seconds
Status Job ID Name Coverage
  Test
passed #6204
MultiThreads Linux
clang-c++11-Qt4

00:07:08

passed #6208
MultiThreads Linux
clang-c++11-Qt5

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passed #6206
MultiThreads Linux
clang-c++98-Qt4

00:05:54

passed #6210
MultiThreads Linux
clang-c++98-Qt5

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passed #6211
MultiThreads Linux
cppcheck

00:38:55

passed #6203
Linux
gcc-c++11-Qt4

00:03:33

passed #6207
Linux
gcc-c++11-Qt5

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passed #6205
Linux
gcc-c++98-Qt4

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passed #6209
Linux
gcc-c++98-Qt5

00:03:51