Construct a tlist in grocer panel format
pdb = paneldb(ind,var,arg1,...,argn)
* ind = vector of name for individual
* var = vector of generic name for variable
* arg1,...,argn = arguments which can be:
- 'conc = 1' if concatenation must begins by individual names (2 instead, default =1)
- 'bounds =[''bounds1'' ''bounds2'']' bounds for data
* rpdb = a results tlist with
- rpdb('panel data') = type of the list
- rpdb('dates') = bounds of data
- rpdb('id') = individual indentifiant
- rpdb('x') = stacked data in matrix format
- rpdb('nameid') = names of individual indentifiant
- rpdb('namex') = generic names of data