Added vfps command to estimate average frame rate of 3D Viewer
Simplified vdrawsphere command
Removed turnVbo and performance measurements from vdrawsphere.
Added vvbo command to control VBO usage flag.
Changes:
Text rendering in OCCT 3D view can now display multi-line text correctly. In addition to '\n' and '\r' characters, '\t' is also treated specially, i.e. replaced by a fixed number of spaces. Other control characters (like '\b' or '\a') are simply ignored by text rendering code.
Also standard GL2PS's alignment isn't used because it's doesn't works correctly for all formats, therefore alignment is calculated manually now.
