Use static nested classes to reduce unneeded pointers
No harm if http-repo-conn is left open, don't take on overhead of finalizing it
Let iterations and connections be gc'd after closed and track open iterations in connection
Use native store optimized disk-base statement list for update operations to avoid OutOfMemoryErrors
Deprecate forceClose() method
Use TreeSet to filter out duplicates in DELETE/INSERT clauses before realizing them in the memory store
SES-1975 : Update logback

logback-1.0.13 does not contain one of the classes that was in 0.9.28, so this requires a change to the logback configuration class as well as the bump
SES-1977 fix in anonymous SailBase implementation: override of default
isolation level for federations.
Merged in ses-1977 (pull request #228)

SES-1977 fix in anonymous SailBase implementation: override of default isolation level
Merged in SES-1975 (pull request #227)

SES-1975 : Update logback
Merge branch 'master' of bitbucket.org:openrdf/sesame into SES-1957

Conflicts:
	core/sail/api/src/main/java/org/openrdf/sail/helpers/SailConnectionBase.java
Revert "Use TreeSet to filter out duplicates in DELETE/INSERT clauses before realizing them in the memory store"

This reverts commit 2c8d0e91df8b8c1b8cfa157ac2f042aece2ce1e9.
SailBase#getValueFactory maybe null, so use statement constructor directly
Clarify javadoc and fix compatibility of isolation levels
Add SNAPSHOT_READ isolation level
Created new branch SES-1983
Add unit test to confirm claimed isolation levels match behaviour of stores
Merge branch 'SES-1982' of bitbucket.org:openrdf/sesame into SES-1983
Add test for SNAPSHOT_READ isolation level
Add memory and native store isolation level tests