Checksum search should be case insensitive

When doing a search for the sha1 hash I was unable to locate the file I was expecting. The tool I was using was generating an upper case hash string which didn't match.

e.g. for http://search.maven.org/#artifactdetails|org.springframework.ws|spring-ws-core|2.2.0.RELEASE|jar

<dependency>
    <groupId>org.springframework.ws</groupId>
    <artifactId>spring-ws-core</artifactId>
    <version>2.2.0.RELEASE</version>
</dependency>

The lower case hash works
f5de942e30c3c047a273b5bb42cc5c71d3303fcb
The upper case does not.
F5DE942E30C3C047A273B5BB42CC5C71D3303FCB

Acceptance criteria:

• Make the keyword field case insensitive

Technical notes:

• This will require a reindex