Don't use org.eclipse.core.runtime.products extension point

All product's configuration is in .product file and it makes no sense to
duplicate the same setup in plugin.
Relocate icons and splash to the same directory as a product file
Path to icons/splash should be relative to product file
Start org.eclipse.core.runtime bundle automatically

Also drop custom config.ini file as will be generated based on the
product file's data (product id, splash file bundles etc.)
Extract LICENSE.txt, NOTICE.txt and README.txt from org.neo4j.neoclipse bundle

- during package phase, materialize products with
  tycho-p2-director-plugin's materialize-products goal;
- during package phase, unpack required files from just built
  org.neo4j.neoclipse bundle using Ant's unzip task;
- during pre-integration-test phase (instead of package phase, which is
  default), assemble final archives with tycho-p2-director-plugin's
  archive-products goal.
Place LICENSE.txt, NOTICE.txt and README.txt into every product

Materialized products follow such folder structure:

    > tree -d -L 4 repository/target/products/neoclipse/
    repository/target/products/neoclipse/
    |-- hpux
    |   `-- gtk
    |       `-- ia64_32
    |           `-- neoclipse-1.9.1-SNAPSHOT
    |-- linux
    |   `-- gtk
    |       |-- ppc64
    |       |   `-- neoclipse-1.9.1-SNAPSHOT
    |       |-- x86
    |       |   `-- neoclipse-1.9.1-SNAPSHOT
    |       `-- x86_64
    |           `-- neoclipse-1.9.1-SNAPSHOT
    |-- macosx
    |   |-- carbon
    |   |   `-- x86
    |   |       `-- neoclipse-1.9.1-SNAPSHOT
    |   `-- cocoa
    |       |-- x86
    |       |   `-- neoclipse-1.9.1-SNAPSHOT
    |       `-- x86_64
    |           `-- neoclipse-1.9.1-SNAPSHOT
    `-- win32
        `-- win32
            |-- x86
            |   `-- neoclipse-1.9.1-SNAPSHOT
            `-- x86_64
                `-- neoclipse-1.9.1-SNAPSHOT

    27 directories

Place extacted files to every product's root directory using Ant's
parameterized target file names' mappers, compositemapper +
globmapper.

As there is no way to tell a mapper to place a file into every directory
4 levels deep, we have to enumerate all of them explicitly. To find all
such target directories, run:

    > find repository/target/products/neoclipse/ -mindepth 3 -maxdepth 3 -type d
    repository/target/products/neoclipse/hpux/gtk/ia64_32
    repository/target/products/neoclipse/linux/gtk/x86
    repository/target/products/neoclipse/linux/gtk/ppc64
    repository/target/products/neoclipse/linux/gtk/x86_64
    repository/target/products/neoclipse/win32/win32/x86
    repository/target/products/neoclipse/win32/win32/x86_64
    repository/target/products/neoclipse/macosx/cocoa/x86
    repository/target/products/neoclipse/macosx/cocoa/x86_64
    repository/target/products/neoclipse/macosx/carbon/x86

[1] Mapping File Names, https://ant.apache.org/manual/Types/mapper.html
Use Ant's copy target instead of unzip

Unzip doesn't support multiple mappers. Copy target does but requires
more work.
Delete package.sh

All packaging is done by Tycho itself which makes this script obsolete.