Fix ConditionalOnJndi evaluation

Enable ConditionalOnJndi evaluation and add tests that validate it works
as expected

Fixes gh-1820
polishing
Permit to disable JTA using a single property

Disable JTA auto-configuration altogether with a simple property. This
can be useful if the environment is JTA capable but the application does
not require it.

Fixes gh-1457
Polish
Guard default conversion service creation

Update ConfigurationPropertiesBindingPostProcessor to ensure that
the defaultConversionService is only created once.

Fixes gh-1822
Optimize property sources pattern matching

Create a PropertyNamePatternsMatcher strategy interface that
PropertySourcesPropertyValues can use to determine when a property
can be used.

PropertiesConfigurationFactory uses DefaultPropertyNamePatternsMatcher
which is heavily optimized for frequent calls.

Fixes gh-1823
Add XML support to PropertiesPropertySourceLoader

Fixes gh-1777
Closes 1783
Add PropertiesPropertySourceLoader test
Merge pull request #1783 from Loki-Afro/gh-1777

* gh-1777:
  Add PropertiesPropertySourceLoader test
  Add XML support to PropertiesPropertySourceLoader
Support PID file location in Spring Environment

Update ApplicationPidFileWriter to support the Spring Environment,
picking up the `spring.application.pidfile` property if specified.

Fixes gh-1579
Add fork option for mvn spring-boot:run

Update RunMojo to include a `fork` option and change the default
to only fork if agent or jvmArguments are specified.

Fixes gh-1412
Merge pull request #1483 from liujiong1982/spring-boot-1412

* spring-boot-1412:
  Add fork option for mvn spring-boot:run

Closes gh-1483
Fix typo
Use the Mongo starter for the sample application

See gh-1831
Ensure meta-data file exists for spring-boot jar

Rename 'additional-spring-configuration-metadata.json' to
'spring-configuration-metadata.json' and drop the annotation processor.

The project has no @ConfigurationProperties defined so the annotation
processor didn't kick in.

Fixes gh-1830
Add check-template-location properties to appendix

Some were missing, some were named incorrectly.

See gh-1827
Merge branch '1.1.x'
Fix debug logging

Fix an issue where debug logging never occurred because it was guarded
incorrectly using isWarnEnabled().

Fixes gh-1780
Merge branch '1.1.x'
Update pidfile property and add documentation

Change the pidfile property from `spring.application.pidfile` to
`spring.pidfile` (to save confusion with SpringApplication properties).

Also added documentation and meta-data information.

See gh-1579