Create demo for a two-link planar manipulator

[irublev]

This issue is a part of issue #53.

[irublev]

What remains to do:

1. To fix the code slightly, namely, remove rand from the code (the code should be deterministic, so that its execution must be the same each time it launched), I mean the following lines:

mSize = 10;
dirMat = 2*(rand(nShape, mSize) - 0.5);
for iElem = 1 : mSize
    dirMat(:, iElem) = dirMat(:, iElem) ./ norm(dirMat(:, iElem));
end;

(please see how the same place is changed in the script products/+elltool/+doc/+snip/s_chapter06_section06_snippet01.m in the branch issue_55_mzaitceva_yashalnov_eshevchenko).

2. Renaming of variables should be done:
   linSys -> linSysObj,
   nShape -> nDims,
   rsTube -> rsTubeObj,
   v1v2Mat -> velBasisMat,
   prTube -> prTubeObj

3. It is necessary to do what described in the items 4 and 5 from the text of issue Create more demo examples in documentation #53. It should be stressed that the pictures generated by the function(s) implemented in the item 4 of issue Create more demo examples in documentation #53 should be created anew (according to the item 5 of issue Create more demo examples in documentation #53) and should replace those currently placed in /doc/pic/.