Add function mortalityImprovement to calculate age-specific yearly log-mortality improvements (aka. mortality trends)

- mortalityTables.list and mortalityTables.load can be given multiple packages (defaults to "MortalityTables" and "MortalityTablesPrivate")
- mortalityTables.load supports wildcards in its default call (no need for the wildcard=TRUE argument)

Move anwartschaften.R to the pensionstafel project (forgot to update build system)

- add periodTransitionProbabilities (and use it in anwartschaften)
- add pensionTableProbArrange to build the return data.frame or list for transitionProbabilities

- mortalityTable.zeroes: Generate a mortality table with all zero transition probabilities
- mortalityTable.once: Generates a (deterministic) mortality table with one transition at a given age
- pensionTables.list: Lists all pension tables (similar to mortalityTables.list)
- pensionTables.load: Load a provided pension table (similar to mortalityTables.load)
- transitionProbabilities: Obtain data.frame containing all transition probabilities for a pension table (given the YOB)
- anwartschaften: First attempt to calculate all "Anwartschaften" for a given pensionTable - WORK IN PROGRESS, NOT FINISHED

Allow one table or a list of tables to be passed as the table argument to mortalityTable.jointLives. This allows different insured to have different life tables (e.g. male + female)

Joint life tables (on first death) for now have a maximum age taken from the first insured person (i.e. the first table).

The reason is a purely technical one: The ages of the insured are not part of the table, so the getOmega function does not know any ages. Only the deathProbabilities function gets the actual ages.

This makes it impossible to create tables, where e.g. the last value is repeated as needed. Instead, we will always cut off the table at the maximum age of the table for the first insured person.

The different insured persons are identified by their age difference to the first insured. Different base tables for each insured can be given, by default the same table is used for all insured persons.

# Conflicts:
#	R/mortalityComparisonTable.R
#	man/mortalityComparisonTable.Rd

Add mortalityComparisonTable to create a nice table showing the relative mortalities for age groups and various birth years

extend mortalityTables.load and mortalityTables.list by a "package" argument to allow loading sample data from other packages

The mortalityTAbles.list and mortalityTables.load functions now have an additional parameter package, where one can give a third-party package that holds the dataset in extdata/MortalityTables_....R

CRAN requires that all parameters from the function signature (and only those parameters, no others!) are documented. If we want to document other parameters that are matched by ..., then one cannot use @param. So we simply created a nested list and explicitly list those params in a describe list.

Also rename the classes to mortalityTable.*