PDRplan version 1.2

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- inductive minimization inside extend (-m=2 and -m=3)
- extend no longer support returning more than one learned clause
- removed the flag for multiple extensions and simplified the code accordingly
- noop_from_current is now the only possibility for ensuring monotonicity (the flag was removed)
- resolved compiler issues (see makefile)

v1.1: PDRplan version 1.1

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- a planning specific, dynamic ordering for traversing actions in extend replaces the original randomized one
- obligations kept between phases by default (main.c)

v1.0: PDRplan version 1.0

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Supported features in Main.cpp include:
- explicit reason minimization
- clause subsumption
- clause propagation
- reverse mode (with invariant generation)
- the quickreason trick
- sidestepping extensions
- keeping obligations during phases (iterations)

Other modified files:
bb.h, main.c
- new command line flags declared and parsed
output.[h,c]
- added a function print_GroundedFactToFile
.gitignore
- ignore planning related files and other temporaries
Makefile
- added the new c++ sources

Added files:
Translate.[h,cc]
- support for simple translation into dimspec format a la "encoding into SAT" with sequential and parallel plan semantics
- support for grounding a pddl input; compatible with reverse mode -> can be used to obtain dual versions of pddl benchmarks
Invariant.[h,cc]
- support for the computation of binary clause reverse invariants (properties of the goal preserved backward by the transitions);
  this is mostly used in reverse mode where it boils down to the traditional invariants
Common.[h,cc]
- common interfaces to access actions inside "bb", print them, etc...