[jinterface] add Eclipse projects and settings

For other IDEs, use these as reference. In short, the formatting
style is:

- indentation uses only spaces; each level is 4 positions
- no trailing whitespace
- mostly default Java style formatting (any difference is minor)

- always use {}
- use 'final' as much as possible
[jinterface] cleanup code according to new style
asn1: Fix EXTERNAL (1994 variant) type conversion

Missed to add seqtag handling for EXTERNAL type conversion,
bug introduced in c266196c016fc1156c7a18cfeec4920ee4075519
Merge branch 'dgud/asn1/fix-seqtag/OTP-12326' into maint

* dgud/asn1/fix-seqtag/OTP-12326:
  asn1: Fix EXTERNAL (1994 variant) type conversion
Merge branch 'maint'
Merge branch 'vladdu/jinterface_format/OTP-12333'

* vladdu/jinterface_format/OTP-12333:
  [jinterface] cleanup code according to new style
  [jinterface] add Eclipse projects and settings