... and remove unnecessary 'Bundle-ClassPath: .' entries.

Replace the use of the legacy and Eclipse-specific MANIFEST.MF header
'Eclipse-LazyStart: true' by the OSGi standard compliant header
'Bundle-ActivationPolicy: lazy' (which is already used in most cases.

The default value of 'Bundle-ClassPath' is the dot which is used when
the header is not specified. Therefore there is no need to specify it
with that value.