fix: heuristically choose correct function for minors
add: idKeepFirstK() in ideals.cc

Conflicts:
	Singular/MinorInterface.cc
	kernel/ideals.cc
	kernel/ideals.h
chg: rewrite idDelEquals based on qsort()

Conflicts:
	kernel/ideals.cc
chg: incorporate some suggestions by Hans

Conflicts:
	kernel/ideals.cc
fix: idKeepFirstK (Example_7_3_14)

Conflicts:
	kernel/ideals.cc
fix: const

Conflicts:
	kernel/ideals.cc
Merge pull request #280 from malex984/adapting_commits_from_master_minors

Adapting commits from master minors