Add comment why use of old correlation matrix from previous draw is correct and revert change

Due to only using the diagonal of Sigma_e and the correlation matrix having ones on the diagonal, the diagonal entries of the covariance matrix are correctly built from recent draw. Later, when using the new draw for the correlations, only the correctly updated diagonal entries of Sigma_e are used.
Fix several bugs related to estimated measurement errors

1. The first call to set_prior overwrote the first column of
estim_params_.var_endo storing the position of the variable with
measurement error in M_.endo_names with the position in
options_.var_obs. All subsequent calls to set_prior then lead to
crashes.
2. At the same time, for correlations of ME, the first column of
estim_params_.corrn still stored the position of the variable with
measurement error in M_.endo_names. But subsequent calls to it were done
as if it stored the position in options_.var_obs

I introduced two new variables in estim_params_ storing the respective
positions in var_obs so as to not necessitate changes in the
preprocessors.

3. For cases of calibrated measurement error correlations, the
covariance matrix was not updated.

4. Fixing a lot of smaller bugs related to measurement errors, including
some copy and paste errors
-
Add unit test for correlated measurement error

Tests both ML and Bayesian estimation and test calibrated correlation of
those shocks
Clarify treatment of measurement error and correlations in manual
reporting: @table: vlines
reporting: @table, @graph: require data to be dynSeries, simplify checks
reporting: spacing cleanup
reporting: @vspace
Changed behaviour of @dynDates/display.
Added @dynDates/union function.
Added a routine to convert variable names with underscores into somthing readable by a tex processor.
Deduce tex names from the names of the variables in dynSeries objects.
Make load and save routines for dynSeries objects support tex variable names.
Changed behaviour of @dynSeries/uminus and fixed bug.

 + Prefix variable names with the minus symbol.
 + Set tex member.
Changed copyright year.
Changed behaviour of @dynSeries/ydiff (name  of the variables).

 + Prefix variable names with YDIFF_
 + Prefix tex variable names with \Delta_i with i=nothing, 4, 12 or 52 depending on the frequency.
Added unitary test for @dynSeries/ydiff.
Changed behaviour of @dynSeries/qdiff (name  of the variables).

+ Prefix variable names with QDIFF_
+ Prefix tex variable names with \Delta_i with i=nothing or 3 depending on the frequency.
Changed behaviour of @dynSeries/ygrowth (name  of the variables).

 + Prefix variable names with YGROWTH_
 + Prefix tex variable names with \delta_i with i=nothing, 4, 12  or 52 depending on the frequency.
Changed behaviour of @dynSeries/qgrowth (name  of the variables).

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