Fix of checking existence of group when creating new one

- add parentGroupId to checking of group existence
- add test for two same groups with the same name,parentGroup and voId
Unified workflow with empty string and null in setAttributes and setAttribute
 - Added method convertBlankStringIntoNullInAttrValue into AttributesManagerBl
 - Modified methods setAttribute and setAttributes in AttributeManagerEntry
   - convertBlankStringIntoNullInAttrValue convert empty string into null for checkAttributeValue and checkAttributeExists() to unify work with empty string and null
 - Some database are not able to recognize empty string and null. This is the reason why we convert empty string into null in entry.
CORE: fixed implementation of delete password method

 - delete password only when reserved by registrar
 - do not delete password when reserved by attribute or not reserved at all

 Previous wrong behavior

  - if not reserved by both attribute and registrar -> delete password
  - if reserved only by attribute -> throw exception
  - if reserved only by registrar or both -> do nothing
Merge pull request #253 from zlamalp/deletepassword

CORE: fixed implementation of delete password method
Added more information into exception in UF:V:login
 - exception now carry important attributes
Description of tables and columns added

- use postgre comments in postgre.sql (-- instead of #)
- Locale columns
- add description for all tables in postgre.sql
- alter tables:
ALTER TABLE pn_receiver ADD locale varchar(512);
ALTER TABLE pn_template DROP COLUMN locale;
ALTER TABLE pn_pool_message DROP COLUMN locale;

-alter destination table: (add propagatio_type)
alter table destinations add propagation_type varchar(10) default 'PARALLEL';
GUI: Enable GWT 2.6.0

- Update GWT 2.5.1 -> 2.6.0
- Added ie10 permutation.
- Should bring better performance and stability
  to both dev-mode and runtime.

- Fixed issue in PerunAttributeCell when event.currentTarget
  was not filled by jQuery, but was required by GWT to handle
  events. So now removing value from list/map attributes in
  table correctly calls update to the attr object itself.
- Source format of PerunAttributeValueCell.
Merge pull request #261 from zlamalp/gwt26

GUI: Enable GWT 2.6.0
GUI: prevent doubling exception ID

- Do not display error ID in report widget twice (as part of heading).
  ID is displayed by UiElements.generateAlert() itself.
Merge pull request #263 from zlamalp/fix

GUI: prevent doubling exception ID
Merge pull request #258 from papperwing/attributeHolders

- Added more information into exceptions in UF:V:login.
- Prefer throwing WrongAttributeValueException instead of WrongReferenceAttributeValueException
  since in module, we can tell if:
  - facility's namespace is empty (login can't be determined) or
  - user doesn't have login in facility's namespace (null or non-unique). 
 Other cases are handled by standard exceptions (Consistency, AttributeNotExists etc.).
Merge pull request #250 from stavamichal/create_group_existence_checking_fix

Fix of checking existence of group when creating new one
Fix bug in delay of repropagation of tasks in DONE

Tasks in DONE should be repropagated each 2 days unless some event
trigers it earlier. Because of faulty constant they were repropagated
each 48 minutes.
Inicial import of perun slave services
GUI: allow dot in VO shortName
Merge pull request #266 from zlamalp/dot

GUI: allow dot in VO shortName
Merge pull request #260 from zoraseb/table_documentation

Description of tables and columns added
Merge pull request #229 from papperwing/BlankString

Unified workflow with empty string and null in setAttributes and setAttribute