Commits on May 9, 2018

1. ENHANCE: Reduce impact of immediate methods for groups etc. …

   This commit changes routines that create groups, certain Submagmas aand
   vector spaces so that flags that set basic properties (being trivial, being
   empty, being cyclic) are set at the same time as the object was created.
   
   This functionality used to be provided through immediate methods, however
   this meant that the type of a just-created object was changed immediately
   multiple times (with some changes precipitating other changes), causing a
   notable performance hit.
   
   Notably, the following changes have been done:
   
   1) In a number of methods used to create groups (or submagmas, when called
   from `Subgroup` or cosets) from generating sets, a number of cheaply deduced
   properties (such as being cyclic) are set while creating the object. Thus
   the immediate methods do not apply for these objects any longer.
   
   2) Type caching in these methods is not worth the effort and has been
   removed.
   
   3) A new setter method for `Size` deals similarly with deductions done
   before by immediate methods for a known size.
   Caveat: The manual specifies (ill-advised one might say) that setting a
   different size if a size already is given will be ignored. This is tested in
   manual examples and test files. The new setter method therefore cannot be
   used to check for this property as an error -- it will do so only if
   assertion level is set >=3.
   
   4a) Immediate methods that have been made obsoleteby the changes in 1) and 3)
   have been changed to ordinary methods.
   
   4b) A number of immediate methods (e.g. a trivial group is solvable) have
   been replaced by `TrueMethods` that have the same effect but are chaper to
   run.
   
   4c) Also a number of immediate methods
   that need to run often, but apply only rarely (i.e. setting `IsFinite` to
   false if a size is set to `infinity`) have been removed.
   
   5) These changes have minor impact on test files and manual tests: A few objects
   will have slightly different knowledge about their properties  and thus
   print differently; respectivelty test code exists that checks explicitly for
   such properties having been set by immediate methods.
   These tests and examples have been changed.
   A few, very instable tests (e.g. checking explicitly for the values of
   random elements) have been commented out.
   
   6) Some tests explicitly relied on immediate methods enabling derived series
   calculations in special cases of finitely presented groups. These tests
   never would have worked if immedite methods were turned off, the respective
   finitely presented groups method has been changed accordingly to test
   explicitly for the particular situation, thus enabling the same examples to
   work.

   

   hulpke committed May 9, 2018
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