Print nice error in bin/elasticsearch if user needs to run maven

Before, people that cloned the repo and expected to be able to run
bin/elasticsearch would be met with an awful shell error: the shell
interprets Maven variables like ${project.build.finalName} as shell
variables yet can't handle names of the form ${x.y}. This commit
explicitly checks to make sure that Maven has done its substitutions
before continuing; if Maven hasn't been run, it gives a helpful error
message.

Fixes #2954.

bin/elasticsearch

@@ -46,6 +46,20 @@
 # Be aware that you will be entirely responsible for populating the needed
 # environment variables.
 
+
+# Maven will replace the project.name with elasticsearch below. If that
+# hasn't been done, we assume that this is not a packaged version and the
+# user has forgotten to run Maven to create a package.
+IS_PACKAGED_VERSION='${project.name}'
+if [ "$IS_PACKAGED_VERSION" != "elasticsearch" ]; then
+    cat >&2 << EOF
+Error: You must build the project with Maven or download a pre-built package
+before you can run Elasticsearch. See 'Building from Source' in README.textile
+or visit http://www.elasticsearch.org/download to get a pre-built package.
+EOF
+    exit 1
+fi
+
 CDPATH=""
 SCRIPT="$0"