- maintenance: removing references in the vignettes to csl-file as this caused an error

- using the Stabilized MMR formula for maternal mortality
- adding the possibility to calculate population size from skeletal populations
- adding more reproduction indices

- adding an option for plotting in color instead of linetype
- adding more functions for checking representativity of age data, calculating reproduction indices, masculinity index, maternal mortality rate as well as corrected life tables
- major re-factoring
- rewriting of tests to work with testthat’s new snapshot-functionality
- adding two vignettes for life table correction and reproduction indices

- tweaking the class-functions so that class mortaar_life_table is maintained when manipulating a mortaar_life_table_list
- adding a spline-option when constructing the life table for smoother adult age-groups

- rewriting of some of the basic code
- defining of “class_functions.R”
- dividing of “output_functions.R” into “analytical_functions.R” and “plot_functions.R”
- fixing of some typos in the documentation and the output
- fixing of a small but serious bug which caused a non-alignment of the curves with the x-axis in the plots

First release.