Names for the results of basic operations on dynSeries objects was '--NA--'. The name of the result
variables now keep track of the operations. For instance, if we have two dynSeries objects, ts1 and
ts2, respectively holding two variables 'A1' and 'B1', then:

 - the name of the variable in ts3=ts1+ts2 is 'plus(A1,B1)'
 - the name of the variable in ts3=ts1-ts2 is 'minus(A1,B1)'
 - the name of the variable in ts3=ts1*ts2 is 'multiply(A1,B1)'
 - the name of the variable in ts3=ts1/ts2 is 'divide(A1,B1)'
 - the tex name of the variable in ts3=ts1+ts2 is '(A1+B1)'
 - the tex name of the variable in ts3=ts1-ts2 is '(A1-B1)'
 - the tex name of the variable in ts3=ts1*ts2 is '(A1*B1)'
 - the tex name of the variable in ts3=ts1/ts2 is '(A1/B1)'

Returns zero if the input argument is a well defined dynSeries object.

 + Added the possibility to rename the assigned variables.
 + Added unitary tests.

Issue an error if two dynSeries objects with common variable names are concatenated. Added a unitary test.

Compare two one dimensional cells of strings and count the number of common strings. The
optional second argument returns a formated list of common variables.

*Example*

If we have:

A = {'A1'; 'A2'; 'A3'; 'A4'; 'A5'; 'A6'};
B = {'B1'; 'A2'; 'B3'; 'A4'; 'A1'};

then

[n,message] = common_strings_in_cell_arrays(A,B);

returns n=3 and message='A2, A4 and A1'.

Removes a variable form a dynSeries object.

If the names of the variables are not provided when instantiating a dynSeries object
then the default name is of the form Variable_i (i=1,...,N, where N is the number of
variables in the dataset).

+ Prefix variable names with QGROWTH_
+ Prefix tex variable names with \delta_i with i=nothing or 3 depending on the frequency.

 + Prefix variable names with YGROWTH_
 + Prefix tex variable names with \delta_i with i=nothing, 4, 12  or 52 depending on the frequency.

+ Prefix variable names with QDIFF_
+ Prefix tex variable names with \Delta_i with i=nothing or 3 depending on the frequency.

 + Prefix variable names with YDIFF_
 + Prefix tex variable names with \Delta_i with i=nothing, 4, 12 or 52 depending on the frequency.

 + Prefix variable names with the minus symbol.
 + Set tex member.

Added a routine to convert variable names with underscores into somthing readable by a tex processor.