Display error in case home source directory is not accessible

[litvinovg]

What does this pull request do?

Added custom exception in case home source directory doesn't exist (could happen in case tomcat application redeployment fails).

How should this be tested?

• Build and install VIVO
• Manually delete directory tomcat/webapps/${app-name}/WEB-INF/resources/home-files
• Restart tomcat
• Open VIVO
• You should see error report containing error description and instruction how to solve the issue.
• Follow instructions and check if that fixed the issue.

Interested parties

@brianjlowe @chenejac

Reviewers' expertise

Candidates for reviewing this PR should have some of the following expertises:

1. Java

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[chenejac]

@litvinovg works for me. Thanks for this improvement.

[brianjlowe]

Looks good